It is known in the art that in high power applications (e.g. over 1 MW), a medium voltage (i.e. higher than 1 kV) presents certain advantages over the low voltage in heavy-duty electric machines, due to lower current levels. In case that the shaft rotational speed needs to be controlled, a speed controller, such as a frequency converter, naturally needs to be designed for the same medium voltage level.
To ensure the user safety and the functional safety of the electric circuit, the hazardous parts of the devices connected to an electricity network must be protected in accordance with international safety standards like UL347A and IEC61800-5-1. The safety is ensured by arranging sufficient electric isolation around the live parts by using clearances, creepage distances or barriers made of an insulating material.
In power electronic constructions, the heat sink or other metal structure often works as a base element (of e.g. a power module), whereto the power components, supports for bus bars, insulating shrouds etc. are attached. When using typical, traditional and today common mounting methods, the power electronics device is placed inside a conductive metal housing that is grounded for safety reasons. In case of e.g. a power electric apparatus, like in examples of FIGS. 1 and 2, this means that every energized component or power module requires separation from the frame parts and walls of the housing etc. by long clearances and tall standoff insulators, thereby requiring substantial volume within the electric device to accomplish the required isolation. In addition, e.g. in service situations, a special care must be taken to ensure the integrity of the isolation arrangements and that no electrical faults or clearance violations occur to the housing of the power electric device.